The adjustable ring of contractile and
connective tissues that controls the amount of
light entering the eye is the
a. lens.
b. cornea.
c. pupil.
d. iris.
e. retina.
D
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The organ responsible for excretion of both
urine and feces indicated by the letter"F" is called the a. mouth. b. crop. c. gizzard. d. secreting portion of stomach. e. cloaca
Crossing over is __________.
A. the formation of tetrads B. the exchange of corresponding portions of homologous chromosomes C. the movement of genetic material from one chromosome to a nonhomologous chromosome D. an independent assortment of chromosomes
________ occurs as ________ builds up in the system if Enzyme A is nonfunctional because of an inherited mutation. 
A. albinism; melanin B. androgen insensitivity; tyrosine C. xeroderma pigmentosum; tyrosine D. phenylketonuria; phenyalanine
Australopithecus was the first hominin to feature which distinguishing characteristic?
a. bipedalism
b. larger brains c. shorter arms d. sexual dimorphism e. facultative bipedalism